1. Field of the Invention
This invention relates to an inner handle assembly of a cylinder lock, more particularly to an inner handle assembly which incorporates a manually operable lock unit that can lock a door from the inside of the door without using any key so as to prevent opening of the door from the outside.
2. Description of the Related Art
Generally speaking, a conventional cylinder lock includes inner and outer handle assemblies mounted respectively to two opposite sides of a door, and a spindle connecting the inner handle assembly to the outer handle assembly for actuating a bolt of the cylinder lock by virtue of operation of the inner handle assembly or the outer handle assembly in order to open the door. The conventional cylinder lock further includes a manually operable lock unit installed on the inner handle assembly and to be operated from the inside of the door without using any key so as to prevent opening of the door from the outside. The releasing operation of the conventional door lock is conducted by turning an inner handle of the inner handle assembly or an outer handle of the outer handle assembly so as to rotate the spindle to actuate the bolt after the lock unit is moved to its unlocking position. In case the manually operable lock unit is to be unlocked, the push button of the lock unit has to be pulled manually prior to turning of the inner handle or the outer handle. Accordingly, it is quite. inconvenient to operate the conventional door lock.
In order to improve the above described drawback, U.S. Pat. No. 5,083,823 has disclosed a latch bolt operating device to be mounted to a door. As disclosed, the latch bolt operating device includes a manually operable locking shaft installed between outer and inner handle assemblies of the latch bolt operating device for locking the door without using any key, an inner spring-loaded rotary plate mounted to an inner handle of the inner handle assembly for rotating simultaneously therewith, and a cam member provided on the rotary plate for camming the locking shaft to its unlocking position when the rotary plate is rotated by virtue of turning of the inner handle, thereby unlocking the latch bolt operating device.
However, since the manually operable locking shaft is interconnected to the inner and outer handle assemblies, when it is desired to mount the latch bolt operating device to a door, the inner and outer handle assemblies of the latch bolt operating device have to be mounted precisely at predetermined positions of the door in order to facilitate installing of the locking shaft between the inner and outer handle assemblies. Accordingly, it is quite inconvenient to mount such latch bolt operating device to the door.